A serotonin 2C (5-HT2C) receptor is one of the receptors for serotonin, a transmitter related to various physiological functions in the biological body. Its expression has been recognized mainly in the central nervous system (brain/spinal cord).
An anorectic action is known as a physiological function of the central 5-HT2 receptor, and the lowering action of various 5-HT2 receptor agonists on food intake has been reported in rats (Non-Patent Documents 1 and 2). Further, it has been confirmed that an anti-obesity action in humans is exhibited due to the anorectic action of the 5-HT2C receptor agonist (Non-Patent Document 3).
The central 5-HT2C receptor is involved in the control of peripheral nerve functions and it has been reported that the rat penile erection is induced by a 5-HT2C receptor agonist (Non-Patent Document 4) and that the time taken from insertion to ejaculation in the experiment for mating behavior of monkeys is prolonged (Non-Patent Document 5). Moreover, it has been reported that a 5-HT2C receptor agonist increases the urethral resistance when the abdominal pressure is increased in rats (Non-Patent Document 6). In addition, it has been reported that in disease models with neuropathic/inflammatory pain in rats, efficacy is exhibited by intraspinal administration of a 5-HT2C receptor agonist (Non-Patent Documents 7 and 8). Various clinical applications are considered for 5-HT2C receptor agonists, particularly as anti-obesity drugs, drugs for treating male erectile dysfunction, drugs for treating premature ejaculation, drugs for treating stress urinary incontinence, drugs for treating neuropathic/inflammatory pain, or the like.
As the 5-HT2C receptor agonist, a benzazepine derivative has been reported, and as a tricyclic benzazepine derivative, for example, Compound A (Patent Document 1) and Compound B (Patent Document 2) are known.

As other 5-HT2C receptor agonists, bicyclic benzazepine derivatives have been reported (Patent Document 3, Patent Document 4, and Patent Document 5).
As a 2,3,4,6,7,8,9,10-octahydro-1H-azepino[4,5-g]quinoline derivative or a 3,4,6,7,9,10-hexahydro[1,4]oxazino[2,3-h][3]benzazepine derivative, which is a tricyclic benzazepine derivative, a compound of the formula (AA) is known to be a Dopamine D3 modulator and be useful for central drug abuse and drug dependence (Patent Document 6).

In addition, in this document, the following compounds are disclosed as a synthetic intermediate for the formula (AA).

Furthermore, there is a report on the structure-activity relationship of a specific compound of the formula (AA) (Non-Patent Document 9), and in this report, it is described that the following compound was used in the preparation of the compound of the formula (AA).

Moreover, there is a report on a 5-HT6 receptor antagonist (Non-Patent Document 10), and it is disclosed that for the compound below, potency on the 5-HT6 receptor is lost by changing a ring condensed with benzazepine from a 5-membered ring to a 6-membered ring.

However, in the documents which disclose such tricyclic benzazepine derivatives, there is no disclosure on the 5-HT2C receptor agonist activity of the 2,3,4,6,7,8,9,10-octahydro-1H-azepino[4,5-g]quinoline derivative or the 3,4,6,7,9,10-hexahydro[1,4]oxazino[2,3-h][3]benzazepine derivative.